Theoretical Study On Doping Cluster Of [Au₂₅（PR₃）₁₀（SR）₅Cl₂]²⁺,Au₂₅（SR）₁₈^- And Ag₂₅（SR）₁₈^-

Thanks to their particular properties such as magic stability,surface effect,catalytic performance,as an interdiscipline,the science of clusters was became a hot research topic early,and its development momentum is very rapid.Noble metal clusters,such as gold clusters and silver clusters,become one of the best of clusters family benefit from their outstanding physical and chemical properties and wide applications in many fields,such as catalysis,biomedicine and so on.They arouse keen interest of researchers,and the related studies are enduring.The existence of the synergistic effect makes some properties of alloy have greatly improved when compared with homologous pure metal.Inspired by this,cluster research has a new direction.The study found that compared with the pure metal clusters,alloy clusters have some unique properties.In addition,the physical and chemical properties of the clusters can be adjusted by changing its arrangement or size.Therefore,alloy clusters have a wider range of applications.In this paper,density functional theory（DFT）which is based on the first principles method is used to predict and study the heteroatom doping of[Au₂₅（PR₃）₁₀（SR）₅Cl₂]²⁺,Au₂₅（SR）₁₈^- and Ag₂₅（SR）₁₈^-（R-is an alkyl group）theoretically.The main contents of the paper can be divided into two parts.One is study on structures,evolution law of structuresandspectroscopicpropertiesofmultitudinousisomersof[Ag_nAu_25-n（PR₃）₁₀（SR）₅Cl₂]²⁺（n<14）.The other is study on the structures,structures’s evolution law,magnetic properties and binding energy of M@Au₂₄（SR）₁₈^- and M@Ag₂₄（SR）₁₈^-（M is a transition metal atom）.In the first part of the thesis research content,we study the situation of single atom andmultipleatomsdopingofstick shaped,doubleicosahedral[Au₂₅（PR₃）₁₀（SR）₅Cl₂]²⁺.The doped atoms are silver atoms,the number of doped atoms from 1 to 13.Only in a small number of situations,the number of isomers is small.In other cases,there are a lot of isomers.When the number of Ag from 1 to 5,we constructed all of its isomers.By density functional theory（DFT）,the optimal structures are obtained by optimization.Then position of the corresponding silver atoms in the most stable structures of each doped atom number is summarized by us.Summarizes the existing law from the study which the number of Ag atoms from 1 to5,together with other researchers relevant results,we knew that the bond Au-P is more stable than Ag-P.Therefore,we can abandon those structures which contain Ag-P bond.Hence,the preferential doping position of the silver atoms is located at both ends of the central axis and the midpoint of central axis as well as the interior of two five-membered rings near the midpoint.According to this rule,silver atoms of the isomers were located in this region in the following study.After structural optimization,we summarized the position of the silver atom in the most stable structures in the case of each number of doped atom,and then summarized the structure evolution law.Subsequently,we calculated the displacement energy of different numbers of silver atoms.The result showed that displacement energy（i.e.,?E）was increased with the number of silver atoms.It also indicated that the stability of alloy clusters decreased with increasing number of silver atoms.In the study of the nature of electronic excitation,we first calculated the electron density of HOMO and LUMO of clusters and the calculation results showed that when the alloy clusters doped with 13 silver atoms,the electron density distribution of the HOMO and LUMO on the central axis was balanced,and mainly distributed in clusters,with good symmetry.While the silver atoms number less than 13,HOMO and LUMO of clusters do not show the distribution of such situation,this is also a reason for alloy cluster doped with 13 silver atoms possess strong fluorescence.Then the spectral properties of the most stable structures were calculated.The calculation results showed these clusters have two distinct absorption peaks and the number of silver atoms had little effect on the wavelength of the first absorption peak,but had a greater influence on the wavelength of the second absorption peak.As a result,we knew that the cluster of[Au₂₅（PR₃）₁₀（SR）₅Cl₂]²⁺had high activity for Ag atoms doping and could replace a number of gold atoms of gold cluster.The first doping position of the silver atom was the two ends and the middle point of the central axis of the cluster,followed by the interior of two five-membered gold rings near the midpoint.In the second part,the main body of the thesis are Au₂₅（SR）₁₈^- and Ag₂₅（SR）₁₈^-,which are made up of respectively an icosahedral Au₁₃ core and Ag₁₃ core with a protective layer of 6 RS（AuSR）₂ staple motifs.Theoretical studies for the single atom doping were carried out and the doped atom is transition metal atom.For each kind of doped atom,the corresponding alloy clusters have three isomers,which are located at the center of the core,the surface of the core and the interior of protected ligands.However,each kind of doped atom possesses many different valence states and spin states commonly.Hence,each kind of doped atom generally corresponds to a variety of cases of different geometric and electronic structures.With the help of density functional theory（DFT）,the optimal structures were obtained.Then magnetic properties,HOMO-LUMO gap and binding energy were calculated.It was found that the doping of Au₂₅（SR）₁₈^- and Ag₂₅（SR）₁₈^- had a large difference.For the cluster of Au₂₅（SR）₁₈^-,most of the transition metal atoms are preferentially located at the center of the Au₁₃ core.However for the cluster of Ag₂₅（SR）₁₈^-,in most cases,the preferential replacement position is located in the interior of protected ligands.In addition,when the doped atom is Pd or Pt,when these atoms are located in the center of core,the structures of alloy clusters are are the most stable.And their large HOMO-LUMO gaps indicate that they are the first choices for the experimental synthesis of M@Au₂₄（SR）₁₈^- and M@Ag₂₄（SR）₁₈^-core-shell alloy clusters.Alloy clusers V@Au₂₄（SR）^q₁₈,Cr@Au₂₄（SR）^q₁₈,Mn@Au₂₄（SR）^q₁₈,Co@Au₂₄（SR）^q₁₈ and Tc@Au₂₄（SR）^q₁₈ which their replacement position was in the center of Au₁₃ core had high magnetic moment.They will be excellent target products for the preparation of magnetic alloy clusters in experiment.Based on the prediction and simulation of the heteroatom doping of these clusters,we get a preliminary understanding of the doping situation of gold and silver clusters,and provide theoretical guidance for subsequent related theoretical and experimental research.